10 folders cost $8.30. Which equation would help determine the cost of 6 folders?
Explanation: There are several equations that could help determine the cost, each with a slightly different approach. We know the cost of 10 folders. We want to know the cost of 6 folders. We can write the numbers of folders as a proportion: $\dfrac{10}{6}$ We know 10 folders costs $8.30. We can let $x$ represent the unknown cost of 6 folders. The proportion of these costs can be expressed as: $\dfrac{\$8.30}{x}$ The cost changes along with the number of folders purchased, and so the two proportions are equivalent. $\dfrac{10}{6} = \dfrac{\$8.30}{x}$